JP4528313B2 - Butt welding method of steel pipe and manufacturing method of welded steel pipe - Google Patents

Description

  The present invention relates to a butt welding method for a steel pipe and a method for manufacturing a welded steel pipe, which can be welded with high efficiency and can provide a sound welded portion without hot cracking.

  As disclosed in Patent Document 1, the applicant of the present invention can easily apply to the manufacture of spiral steel pipes without greatly modifying the equipment, and can greatly improve the efficiency thereof. Proposed.

  In the method for manufacturing a welded steel pipe described in Patent Document 1, first, a submerged arc welding (SAW welding) is performed on the inner surface side of an abutting portion of a hot rolled steel strip bent in a spiral shape at an inner surface welding position by an inner surface welding machine. ), And a steel pipe butt portion surface temperature before outer surface welding is about 400 by energizing a high-frequency induction heating coil (high-frequency heating coil) located on the downstream side of the steel pipe about one and a half times along the weld line. Preheating is performed at a temperature equal to or higher than 0 ° C., and then the outer surface side submerged arc welding is performed at the outer surface welding position by the outer surface welding machine.

JP-A-2006-281313

However, when the method for manufacturing a welded steel pipe described in Patent Document 1 is applied to, for example, butt welding of an axial end surface of a steel pipe, the position of a high-frequency induction heating coil (hereinafter also simply referred to as a heating coil) is fixed. When the inner surface or the outer surface of the steel pipe butt portion is heated by the heating coil, the distance between the surface (inner surface or outer surface) of the steel tube and the heating coil is not constant, and there are the following problems.
(1) Preheating temperature unevenness of the steel pipe butt portion occurs, and the quality of the weld bead portion (bead shape, presence of hot cracking, mechanical properties) is not stable.

(2) When there is a convex part such as a weld bead in the steel pipe butt, the heating coil for high-frequency induction heating (high-frequency heating) and the convex part come into contact, and the butt of the steel pipe cannot be heated properly May occur. In other words, the high-frequency induction heating coil needs to be as close as possible to the inner surface or outer surface of the steel pipe, which is the heating surface, in order to perform efficient heating, but on the other hand, a process for producing a welded steel pipe such as a spiral steel pipe or a straight seam steel pipe In general, the weld bead produced in the above, or the bead in butt welding of a steel pipe, is raised above the surface of the steel pipe, and the heating coil and the weld bead interfere with each other to support the heating coil or the heating coil. Troubles that can damage the body may occur.

  FIG. 6A shows the interference between the weld bead portion BD1 at the start of the steel pipe butt welding and the heating coil 2, and FIG. 6B shows the weld bead portion BD2 of the welded steel pipe and the heating. Interference with the coil 2 is shown. In these drawings, reference numeral 1 denotes a steel pipe, 11 denotes a SAW wire supply nozzle of the submerged arc welding machine 3, 12 denotes a SAW flux supply pipe, and 13 denotes a flux.

  The present invention has been made in consideration of such circumstances. When performing butt welding of a steel pipe while performing high-frequency induction heating, the quality of the weld bead part is stabilized, and the heating coil and the weld bead part are used. An object of the present invention is to provide a steel pipe butt welding method and a welded steel pipe manufacturing method capable of preventing work troubles due to interference.

In order to solve the above-mentioned problem, the steel pipe butt welding method according to claim 1 is a method of joining by performing submerged arc welding while rotating the steel pipe in the circumferential direction after abutting axial end faces of the steel pipe. Then, after preheating at least one of the inner surface and the outer surface including the weld bead portion protruding from the surface of the steel pipe butt portion using a high frequency induction heating coil, the submerged arc welding is performed, and the steel pipe During rotation, the distance between the high-frequency induction heating coil and the inner surface or the outer surface of the steel pipe butt is substantially constant, so that interference between the high-frequency induction heating coil and the weld bead portion is prevented. The high frequency induction heating coil is movably provided at a position in a direction perpendicular to the inner surface or the outer surface of the steel pipe butting portion. A wheel provided in the induction heating coil, by the wheel that is rolled the inner surface or the outer surface of the steel pipe butt section, the relative position in the vertical direction of the high-frequency induction heating coil with respect to the inner surface or the outer surface of the steel pipe butt portion It is characterized by controlling.

According to the butt welding method of a steel pipe according to claim 1, it is possible to heat the butt portion of the steel pipe while maintaining a substantially constant distance between the high frequency induction heating coil and the inner surface or the outer surface including the weld bead portion of the steel pipe. In addition to preventing troubles caused by interference between the high frequency induction heating coil and the weld bead, it is possible to improve the welding work efficiency and stabilize the welding quality.

Further, it provided with freely move the position of the vertical direction relative to the inner or outer surface including a weld bead portion of the high-frequency induction heating coil steel tube, with a simple structure only provided with wheels to the high frequency induction heating coil, a heating coil welding bead Troubles due to the interference of the parts can be prevented, the welding work efficiency can be improved, and the welding quality can be stabilized.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
FIG. 1 is a schematic explanatory diagram of a steel pipe butt welding method according to an embodiment of the present invention.
In this butt welding method for steel pipes, the axial end surfaces of the steel pipes 1 and 1 are butted together and then the steel pipes 1 and 1 are rotated circumferentially by a turning roll (rotating means) 4 while the inner and outer surfaces of the steel pipes 1 and 1 are rotated. The steel pipe butt portions are submerged arc welded by the submerged arc welder 3 to join the steel pipes 1 and 1.
Usually, after welding the steel pipe butt portion on the inner surface side of the steel pipe, the steel pipe butt portion on the outer surface side is welded. Although FIG. 1 shows an example of a butt welding method for a steel pipe on the outer surface side, a similar welding method may be used on the inner surface side.

  In this steel pipe butt welding method, the high frequency induction heating coil 2 installed in front of the welding point (welding position) P is used to preheat at least one of the inner surface and the outer surface of the steel pipe butt portion, and then the submerged arc. Weld. Further, during the rotation of the steel pipes 1 and 1 (during submerged arc welding), the position control means of the high frequency induction heating coil 2 makes the interval between the high frequency induction heating coil 2 and the inner surface or the outer surface of the steel pipe butt portion almost constant. Thus, the relative position of the vertical direction of the high frequency induction heating coil 2 with respect to the inner surface or outer surface of the steel pipes 1 and 1 is controlled.

As a position control means for the high frequency induction heating coil 2, for example, as shown in FIG. 2, the high frequency induction heating coil 2 can freely move in a position in a direction perpendicular to the outer surface (inner surface in the case of inner surface welding) of the steel pipes 1 and 1. The high frequency induction heating coil 2 is provided with a wheel 5, and the wheel 5 is configured to roll on the outer surface (inner surface in the case of inner surface welding) of the steel pipes 1, 1. In this case, the wheel 5 is rotatably attached to a wheel support member 7 fixed to the high frequency induction heating coil 2 by a bolt 6. As in FIG. 6, in FIG. 2, reference numerals 11 and 12 denote a SAW wire supply nozzle and a SAW flux supply pipe of the submerged arc welder 3, and 13 denotes a flux. The positions of the SAW wire supply nozzle 11 and the SAW flux supply pipe 12 of the submerged arc welding machine 3 are fixed.
FIG. 2 shows an example in which the number of SAW wire supply nozzles 11 of the submerged arc welding machine 3 is one, but two or more may be used.

When submerged arc welding is performed by the submerged arc welding machine 3 while rotating the steel pipes 1 and 1 using the high frequency induction heating coil 2 with the wheel 5, even if there is a weld bead portion BD as shown in FIG. The wheel 5 smoothly passes over the weld bead portion BD, and the heating coil 2 integral with the wheel 5 moves in a direction away from the outer surface of the steel pipe 1, so that the interval t between the heating coil 2 and the weld bead portion BD is increased. Since it is kept constant, interference (collision) between the heating coil 2 and the weld bead BD is prevented.

When the groove is provided at the butt portion of the steel pipe 1, the width of the wheel 5 needs to be an appropriate width so as not to be removed from the groove formed by the groove. May be provided across two or more grooves. Although the wheel 5 has to be pressed against the normally steel pipe surface to smoothly roll on the inner surface or on the outer surface of the steel tube 1 during rotation of the steel pipe, when the pressing force than its own weight only is insufficient, springs Ya You may make it press using pressing means, such as a pneumatic cylinder.

  Further, the distance L (see FIG. 3) between the rotation center axis of the wheel 5 and the high frequency induction heating coil 2 follows the weld bead portion (convex portion) BD on the surface of the steel pipe 1 to position the heating coil 2 in a timely manner. In order to control, it is desirable to shorten as much as possible. That is, if the distance L is large, the heating coil 2 is moved away from the surface of the steel pipe 1 long before the heating coil 2 reaches the weld bead portion BD on the surface of the steel pipe.

  In addition, in order to avoid the self-heating and the short circuit by the high frequency magnetic flux which generate | occur | produces from the high frequency induction heating coil 2, the surrounding mounting part of the wheel 5 and a bearing is comprised with the heat resistant insulator (for example, ceramics etc.).

  FIG. 4 is a diagram showing another example of the high-frequency induction heating coil with wheels. In this example, an opening 2a is formed at the center of one side of the rectangular high-frequency induction heating coil 2, and a part of the wheel 5 is inserted into the opening 2a. A pair of heating coil support members 21, 21 are fixed on both sides of the opening 2 a of the heating coil 2, and the wheel 5 is rotatable on these heating coil support members 21, 21 via bearings 22, 22. It is attached. The heating coil support members 21 and 21 are provided so as to be movable in positions perpendicular to the inner surface or outer surface of the steel pipe.

Embodiments of the present invention will be described below with reference to the drawings.
In this embodiment, as shown in FIG. 5, a steel pipe 1 (outer diameter 1600 mm × thickness 42 mm) in which groove processing was performed on the inner and outer surfaces in advance was prepared. The steel pipe 1 is a straight seam welded steel pipe, and the steel material standard is SKK490. The groove shape of the groove portion is a V-shaped groove shape, the groove angle of the outer surface (both groove angles) is 40 °, the depth is 15 mm, and the groove angle of the inner surface (both groove angles) is 30 degrees. The depth was 15 mm.

  Prior to the outer surface welding, firstly, one pass of submerged arc welding (SAW welding) of the axially abutting portion (groove portion) of the inner surface was performed. The welding speed (rotational speed (circumferential speed) of the steel pipe) at this time was 250 mm / min, and the welding conditions were set to a voltage of 40 V with an electric current (alternating current) of 800 A.

Next, using the high-frequency induction heating coil 2 with wheels 5 shown in FIG. 4, as shown in FIG. 1, the high-frequency induction heating coil 2 positioned on the outer surface side of the steel pipe 1 is energized to join the butt portion before external welding. After that, the submerged arc welding of the groove portion was performed at the outer surface welding position by the submerged arc welding machine 3.
In this case, the mounting position in the height direction of the wheel 5 was adjusted so that the distance between the high frequency induction heating coil 2 and the surface of the steel pipe 1 was about 5 mm. Moreover, the high frequency induction heating coil 2 was installed in the position of 75 mm ahead of the welding point (welding position). The output of the high frequency induction heating coil 2 was set to 50 kW. The welding speed (rotational speed (circumferential speed) of the steel pipe) was 250 mm / min, and the welding conditions were set to a voltage of 35 V with a current (DC) of 1100 A. The submerged arc welder 3 is fixed, and the steel pipe 1 is rotated in the circumferential direction by a turning roll (rotating means) 4.

  As a result of the outer surface welding of the steel pipe 1 under the above conditions, when the high frequency induction heating coil 2 passes through the weld bead (convex part) of the straight seam welded steel pipe, and at the final stage of the outer surface welding, the butt welding start part Even when the heating coil arrived at the weld bead portion (convex portion), the outer surface welding operation could be completed without causing a bumping trouble or the like.

  In the above-described embodiment, the high frequency induction heating coil 2 is installed immediately before the welding point (welding position) P of the outer surface welding of the steel pipe 1 (within a distance of approximately 100 mm or less and approximately 20 seconds or less) to butt the steel pipe. However, preheating by the high-frequency induction heating coil 2 with the wheels 5 may be similarly performed before the inner surface welding of the steel pipe 1.

The present invention can be applied to butt welding of various steel pipes including spiral steel pipes .

It is a schematic explanatory drawing of the butt welding method of the steel pipe which concerns on embodiment of this invention. It is a figure which shows the high frequency induction heating coil with a wheel as a position control means of a high frequency induction heating coil. It is a figure which shows the effect | action of the high frequency induction heating coil with a wheel. It is a figure which shows the other example of the high frequency induction heating coil with a wheel, Comprising: (a) is a top view, (b) is A arrow directional view of (a). It is a figure which shows the groove shape of a butt welding part. It is a figure explaining the malfunction of the butt welding method of the conventional steel pipe, (a) is a figure which shows the interference with the welding bead part of a steel pipe butt welding start part, and a heating coil, (b) is a figure of a welded steel pipe. It is a figure which shows interference with a weld bead part and a heating coil.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Steel pipe 2 High frequency induction heating coil 3 Submerged arc welding machine 4 Turning roll (rotating means)
5 Wheel t Distance between high frequency induction heating coil and steel pipe butt

Claims (1)

After joining the axial end surfaces of the steel pipes, the steel pipes are joined by performing a submerged arc welding while rotating in the circumferential direction, and projecting from the surface of the steel pipe butt using a high frequency induction heating coil After preheating at least one of the inner surface and the outer surface including the weld bead portion, the submerged arc welding is performed, and during the rotation of the steel pipe, the high-frequency induction heating coil and the inner surface or the outer surface of the steel pipe butt portion The high frequency induction heating coil is positioned at a position perpendicular to the inner surface or the outer surface of the steel pipe butt so that the interval is substantially constant and interference between the high frequency induction heating coil and the weld bead portion is prevented. The high-frequency induction heating coil is provided with a wheel, and the high-frequency induction heating coil is provided with a wheel, and the wheel is connected to the inner surface of the steel pipe butt. Wherein by rolling an outer surface, butt welding method of the steel pipe, characterized by controlling the vertical relative position of the high-frequency induction heating coil with respect to the inner surface or the outer surface of the steel pipe butt portion.

Images